08 Aug Excavations

Excavations

An excavation is any man-made cut, cavity, trench, or depression in the earth’s surface formed by removing soil. Excavation work can expose employees to cave-ins, falling materials, hazardous atmospheres, underground utilities, water accumulation, mobile equipment, and falls. Because conditions can change rapidly, excavations must be properly planned, protected, and inspected throughout the work.

Before Excavation Begins

Before digging begins, identify and address hazards that could affect the excavation or employees working in or around it.

• Locate underground utilities and installations before excavation begins. Follow applicable state requirements and the 811 utility-location process.
• Identify and protect surface hazards, including buildings, sidewalks, pavement, utility poles, equipment, and other structures that could create a hazard.
• Evaluate soil conditions, excavation depth, groundwater, nearby structures, traffic, vibration, and other conditions that could affect stability.
• Determine the protective system that will be required before employees enter.
• Provide appropriate equipment for safe access, atmospheric monitoring, water removal, and emergency response when required.

Never begin excavation work based solely on the assumption that the ground “looks solid.”

Competent Person Inspections

A competent person must inspect excavations, adjacent areas, and protective systems for evidence of conditions that could result in cave-ins, protective-system failure, hazardous atmospheres, or other hazards.

Inspections must be conducted:

• Before employees begin work.
• Daily before the start of work and as needed throughout the shift.
• After rainstorms.
• After other events that could increase hazards, such as vibration, water intrusion, or changing soil conditions.

Signs of instability may include cracks or fissures, sloughing soil, bulging at the bottom of the excavation, sinking or subsidence near the edge, or soil and rock falling from the excavation face.

If the competent person identifies a hazardous condition, exposed employees must be removed from the hazardous area until appropriate precautions have been taken.

Cave-In Protection

Employees in excavations generally must be protected from cave-ins when the excavation is 5 feet or more in depth, unless the excavation is made entirely in stable rock. Excavations less than 5 feet deep also require protection when a competent person finds indications of a potential cave-in.

Depending on the conditions, protection may include:

• Sloping.
• Benching, where permitted.
• Shoring.
• Shielding with an appropriately designed trench box or shield.
• Another protective system meeting applicable regulatory requirements.

The protective system must be appropriate for the soil classification, excavation depth, anticipated loads, and conditions at the site.

Never enter or work outside the protected area of a trench box or other protective system.

Access and Egress

A stairway, ladder, ramp, or other safe means of egress must be provided in trench excavations 4 feet or more in depth. Employees must not have to travel more than 25 feet laterally to reach a means of egress.

Ladders

When ladders are used:

• Position them on stable surfaces and secure them when necessary to prevent displacement.
• Inspect them before use and remove damaged ladders from service.
• Keep access to ladders unobstructed.
• Where a portable ladder is used to access an upper landing surface, its side rails must extend at least 3 feet above the landing surface, or another secure means of grasping must be provided when the required extension is not possible.
• Use nonconductive ladders where employees or ladders could contact exposed energized electrical equipment.
• Maintain safe climbing practices and do not carry loads that could cause a loss of balance.

Ramps

Structural ramps used solely by employees must be designed by a competent person. Ramps used for equipment must be designed by a person qualified in structural design.

Ramps and runways must be constructed to prevent displacement and should provide a walking surface that minimizes slipping and tripping hazards.

Spoil Piles and Falling Materials

Excavated material, tools, equipment, and other materials can fall into an excavation or place additional pressure on excavation walls.

Keep spoil piles, materials, and equipment at least 2 feet from the excavation edge, or use retaining devices or other effective methods to prevent materials from falling or rolling into the excavation.

Loose rock or soil that could fall onto employees must be removed, scaled back, barricaded, or otherwise controlled.

Water Accumulation

Employees must not work in excavations where water has accumulated or is accumulating unless adequate precautions have been taken.

Depending on the conditions, controls may include:

• Pumps or other water-removal equipment.
• Drainage systems.
• Special support or shield systems.
• Diversion ditches or dikes.
• Other protective measures appropriate for the conditions.

When water-removal equipment is used to control excavation hazards, the operations must be monitored by a competent person.

Following heavy rain or other water intrusion, the excavation must be inspected before employees re-enter.

Hazardous Atmospheres

Excavations can contain oxygen-deficient, toxic, or flammable atmospheres, particularly around landfills, sewers, pipelines, tanks, contaminated soil, or locations where hazardous substances are stored or used.

Where a hazardous atmosphere exists or could reasonably be expected to exist in an excavation greater than 4 feet deep, the atmosphere must be tested before employees enter.

Atmospheric testing should evaluate hazards such as:

• Oxygen deficiency.
• Flammable gases and vapors.
• Toxic gases, vapors, or other airborne contaminants.

Where hazardous conditions are identified, appropriate controls such as ventilation or respiratory protection must be implemented before entry. When ventilation or other controls are used to maintain a safe atmosphere, appropriate monitoring must be performed to verify that conditions remain safe.

Emergency rescue equipment must be readily available where hazardous atmospheric conditions exist or may reasonably be expected to develop, as required by the applicable standard.

Mobile Equipment and Vehicular Traffic

Employees exposed to public vehicular traffic must wear appropriate high-visibility garments.

When mobile equipment operates near an excavation and the operator does not have a clear and direct view of the edge, use a warning system such as:

• Barricades.
• Hand or mechanical signals.
• Stop logs.
• Other appropriate warning methods.

Where possible, grade vehicle approaches away from the excavation.

Employees must not work underneath loads handled by lifting or digging equipment. Employees should also stand clear of vehicles being loaded or unloaded where falling or spilled material could strike them.

Underground Utilities

The estimated location of underground utility installations must be determined before excavation begins.

As excavation approaches the estimated location of a utility, its exact location must be determined by safe and acceptable means. Once exposed, underground installations must be protected, supported, or removed as necessary to safeguard employees.

Treat unidentified underground lines as hazardous until they have been positively identified.

California Excavation Requirements

For work performed in California, additional Cal/OSHA requirements may apply. Certain excavations 5 feet or deeper into which employees are required to descend require a Cal/OSHA permit unless a regulatory exception applies.

California projects must therefore be evaluated for applicable permit and excavation requirements before work begins.

Before You Enter an Excavation

Never enter an excavation unless you know that:

• The required competent-person inspection has been completed.
• The protective system is appropriate and properly installed.
• Safe access and egress are provided.
• Spoil piles and materials are controlled.
• Underground utilities have been addressed.
• Water accumulation is controlled.
• Atmospheric hazards have been evaluated when required.
• Mobile-equipment and falling-material hazards are controlled.

If conditions change, cracks develop, soil begins moving, water enters the excavation, the protective system becomes damaged, or another hazard develops, exit immediately and notify the competent person.

Remember

A trench does not have to be deep to be dangerous, and a cave-in can occur with little or no warning. Never enter an excavation based on appearance or previous experience alone.

Have the excavation inspected, use the required protective system, maintain safe access, and stay alert for changing conditions.